The present invention relates generally to a laser monitoring apparatus and to a method for monitoring the power of a laser beam in real time.
One way to monitor the power of a laser beam at any given point in time during its operation is to monitor the beam in its entirety, e.g., take the laser off line and measure the full power of the beam. Another way to monitor the beam, in real time, is to use relatively complicated beam splitters. Both of these approaches are often inappropriate and unsatisfactory for particular applications of a given laser beam. Prior laser monitoring methods yielded inaccurate measurements and compromised beam quality. The drawbacks to these prior monitoring systems could only be overcome through the use of expensive beam splitters. Moreover, it is difficult to intercept minute quantities of laser light using conventional beam splitters.
The present invention overcomes the aforementioned disadvantages by monitoring the power of a laser beam with an optical fiber, means for isolating a single frequency and means for monitoring the power of a single frequency. Light from the laser beam enters the optical fiber through a fiber wall rather than solely through a fiber opening once it is trapped or coupled into the fiber. Preferably, laser light impinges on the optical fiber in a direction normal to the fiber, whereupon part of the light is intercepted and coupled into the optical fiber. L. S. Watkins in "Scattering from Side-Illuminated Clad Glass Fibers for Determination of Fiber Parameters," Journal of Optical Society of America, Vol 64, No. 6 p. 67, discusses light scattering effects when a laser beam is directed perpendicular to the axis of a glass fiber.
The output beam of some lasers have a single frequency output, while other lasers have a multiple frequency output. Both types of lasers have practical applications.